groves



Aug. 18, 1959 R. c. GROVES FUEL INJECTION SYSTEM 4 Sheets-Sheet 1 Filed Dec. 28, 1955 Inventor .Fwzafd' 6702 CAQM Attorney 1959 R. c. GROVES 2,899,948

FUEL INJECTION SYSTEM Filed Dec 28, 1955 4 Sheets-Sheet 2 Inventor Attorney R. C. GROVES FUEL INJECTION SYSTEM Aug. 18, 1959 4 Sheets-Sheet. 3

Filed 'Dec. 28, 1955 m t n e V n film/a" C Grave's Attofney 1959 R. c. GROVES 2,899,948

FUEL INJECTION SYSTEM Filed Dec. 28, 1955 4 Sheets+Sheet 4 United States Patent FUEL INJECTION SYSTEM Ronald C. Groves, Grandville, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 28, 1955, Serial No. 555,820

26 Claims. (Cl. 123-119) The present invention relates to internal combustion engines and more particularly to the fuel supply means therefor.

In the operation of a so-called spark ignited internal combustion engine, a combustible charge of atomized fuel and air is compressed in a cylinder and ignited by an electrical discharge. In order to obtain the maximum performance and economy from such an engine, it is essential that the charge of air and fuel be accurately mixed in some predetermined proportions and that each of the cylinders receives an identical charge. Although the ratio of air and fuel in the charge for such an engine may normally remain substantially constant over a wide range of operating conditions, it is highly desirable during some operating conditions to modify or change the proportions of the charge. For example in an automotive vehicle,

the engine normally operates at some fraction of its full capacity and at such loads economy is more important than power. Accordingly, while driving these so-called road loads the air-fuel ratio may be lean for maximum economy operation. However, at other times such as idle operation, full load operation and periods of acceleration, maximum economy is of secondary importance and a mixture suitable for maximum power is preferable. In a normal engine the maximum power charge is richer in fuel than the maximum economy charge. Heretofore, engines for automotive and relatesd uses have employed charge forming means that include one or more carburetors mounted on an intake manifold. The carburetor may have one or more venturis therein and a plurality of fuel jets for metering and atomizing the fuel in the charge. The manifold includes a number of induction passages that distribute the charge to the cylinders Where it is ignited. Although such arrangements have operated satisfactorily in the past, in a modern, high performance engine the inherent limitations of such an arrangement become more apparent and in many instances, these limitations materially decrease the amount of power obtainable from the engine. In order to overcome these limitations and thus increase the output of the engine, resort has been had to complicated intake manifolding systems, compound carburetors and multiple carburetor installations. However, in spite of the efforts of the entire automotive industry to perfect the engine charge forming means, even the best systems of this nature employ intake manifolds that do not insure entirely uniform charging of the cylinders, the carburetors employ complicated control linkages and a disproportionate amount of complex compensating devices that make them expensive and troublesome in operation. Moreover, the venturis, complicated intake passages etc., present such a large resistance to the flow of the charge therethrough that the volumetric efliciency of the engine is lowered sufiiciently to substantially decrease the engines perforrnance.

Since all of the foregoing limitations are inherent in such a charge forming system, a tremendous amount of time and effort has been expended to replace the car- 2,899,948 Patented Aug. 18, 1959 buretor with a fuel system in which the fuel is injected into the charge at or immediately adjacent the combustion chamber or intake valve. By injecting the fuel directly into the charge immediately adjacent the point where it will be used, a minimum amount of manifolding will be required for the air. This will allow a more accurate distribution and metering of the fuel and there 'will be less flow resistance that will decrease the volumetric efiiciency. In view of the fact that a fuel injection system has these and several other advantages over a carburetor, a large amount of time and effort has been directed towards developing a satisfactory injection system. So far all of the systems proposed have had several defects. The primary objection has been their inability to accurately meter the fuel over the wide operating range required by a present day passenger car engine. Consequently, as a practical matter, these systems will not operate smoothly, if at all, during idle, part load, and full load operation. Also these systems required a high degree of individual adjustment at the time of installation and a considerable amount of continual precision adjustment or tinkering in order to keep them functioning properly. As a result such injection systems as have been employed have been limited to special applications such as aircraft, racing vehicles, so-called sports cars and other installations where initial expense, maintenance, peculiarities in operation, etc., are of secondary importance. From the foregoing it will be seen that in spite of tremendous efforts of a large number of people, nobody heretofore has satisfactorily developed a fuel injection system that has all of the characteristics that are required to make it suitable for use on a mass produced automobile.

It is now proposed to provide a fuel injection system which is particularly adapted for use on mass produced automotive engines; This system per se and the component parts thereof are not only readily adapted for mass production but also will require a minimum amount of adjustment during installation and operation thereof. In addition, the proposed system is capable of accurately metering the precise amount of fuel required by the engine during all engine operating conditions and delivering this fuel to the engine in a manner that will insure a smooth and continuous operation of the engine at all times. The system includes a unit capable of not only sensing the volume of air being consumed by the engine and the amount of fuel that is being mixed therewith to form the charge but is also capable of maintaining them in the proportions best suited to the engine operating conditions. More particularly, this is to be accomplished by providing a restriction such as a venturi in the induction inlet and a metering restriction such as an orifice in the fuel line that are adapted to create pressure differentials thereacross as the fluids flow therethrough. The magnitude of these pressure differentials will be indicative of the quantities of air and fuel flow. These pressure differentials are directed to pressure responsive means effective to control the quantity of fuel flowing through the fuel restriction and to the engine. Thus the pressure responsive means may be effective to vary the fuel flow until these pressure drops are in some predetermined ratio. During these conditions the air and fuel will be flowing in the desired proportions to form a charge having the desired air-fuel ratio.

Although the fuel demands of most engines require substantially the same air-fuel ratio over at least the major portions of the normal operating range, there are some engines that may perform better if the air-fuel ratio varies slightly as the load varies. Also there may be factors such as flow losses etc., in various portions of the induction system and fuel system that would tend to produce slight errors in the air-fuel ratio unless they are corrected. Accordingly, in order to correct for any such discrepancies in the engine and/or injection system the amount of resistance of one of the metering restrictions may be made to vary. In the present instance this is accomplished by varying the eflective area of the orifice in the fuel line as the load on the engine varies. Although this may be accomplished in numerous ways it is proposed to place this orifice in the center of a diaphragm with a needle valve projecting through the orifice in spaced relation to the edges thereof. It may thus be seen that the diaphragm will have the opposite sides thereof exposed to the fuel pressures anterior and posterior to the orifice. Accordingly, if properly spring biased, the position of the diaphragm relative to the needle valve will be indicative of the fuel flow and thus the engine load. The profile of the needle may be tailored so that as the diaphragm and its orifice moves axially of the needle, the area of the orifice will be varied, thereby effectively compensating for any discrepancies in the fuel demands of the engine and/or the fuel system.

The profile of the above mentioned needle may be tailored to provide any air-fuel ratio desired over the entire operating range of the engine. Since the fuel will always be flowing through this orifice, it has been found preferable that the needle and the associated orifice in the diaphragm provide an orifice area effective to maintain maximum economy operation of the engine. However, there are frequently conditions under which economy of operation is of secondary importance and the maximum power output of the engine is of utmost importance, i.e., during periods of acceleration and during full load operation. Under these circumstances it is advantageous to employ an air-fuel ratio which produces maximum power. In the normal spark ignited engine such a mixture is usually slightly richer than the mixture for maximum economy. Accordingly, an enrichment or secondary metering orifice may be provided in the fuel line in parallel to the variable area or primary metering orifice above described. This secondary orifice when operative will modify the metering effects of the primary orifice and produce a charge having a mixture suitable for obtaining maximum power output from the engine. A control may be provided that will cause all of the fuel to normally flow through only the variable area or primary metering orifice during normal engine operation, thereby producing a combustible charge having proportions suitable for maximum economy operation and that will, when circumstances demand, cause the fuel to flow through both the primary metering orifice and the enrichment or secondary metering orifice to thereby produce a combustible charge having proportions suitable for maximum power operation. It is preferable that the operation of the control for the secondary orifice be automatically actuated. This control is preferably interconnected with the engine in order to automatically sense the periods during which the full power from the engine is desired. It has been found that during normal operation where maximum economy is desired, there is comparatively large vacuum in the intake manifold and conversely when the maximum power is required from the engine, the intake vacuum will be low. Accordingly, it is proposed to provide a control valve in series with the enrichment or secondary metering orifice that is responsive to this intake vacuum. As a result this valve may be closed when the vacuum is high and open when the vacuum is low. Thus it will be seen that when the engine throttle valve is properly opened for normal road loads, the vacuum will be high enough to maintain the control valve closed and all of the metered fuel will flow through the primary orifice and provide a charge suitable for maximum economy operation. When the throttle is moved to increase the load for acceleration or for maximum power operation, the vacuum will decrease sufiiciently for the valve to open and allow the fuel to flow through both the primary and secondary orifices and result in a charge suitable for maximum power operation.

In an automotive engine it is essential that the engine be capable of idling at a comparatively slow speed and also be capable of driving at least a limited load at this slow speed. The amount of fuel and air consumed during such operation is very small compared to the amount consumed during full load operation. As a result any metering means capable of handling the quantities of air and fuel consumed at full load is normally not capable of accurately metering the fuel demands at idle. In addition, it is normally very desirable during idling to provide a charge having a mixture that is somewhat richer than would be produced by the normal metering controls. Since the throttle valve is always closed or nearly closed at or near idle operation, it is proposed to provide idle means that are responsive to the throttle position and will override the normal metering operation of the fuel system whenver the throttle is at or near its idle position. One way in which this may be accomplished is to provide an air bleed having a valve that will open only when the throttle is closed and allow the intake vacuum in the intake manifold to effect the pressure responsive element and override the venturi vacuum. Thus even through the air flow into the engine is too low to produce a metering vacuum at the venturi throat, there will still be a sufiicient vacuum in the pressure responsive means to cause a suflicient fuel flow for operation of the engine. An adjustment may be provided for limiting the amount of the intake vacuum present in the pressure responsive element to produce the fuel fiow normally required for idle operation.

In the four sheets of drawings:

Figure l is a schematic view of a simplified form of an injection system embodying the present invention and illustrating the operational principles thereof.

Figure 2 is a schematic View of a fuel injection system embodying the present invention and showing the parts thereof while they are in position for idle operation of an engine.

Figure 3 is a schematic view similar to Figure 2 but showing the parts of the fuel injection system in position for so-called road load operation of an engine.

Figure 4 is a schematic view similar to Figure 2 but showing the parts of the fuel injection system in position for full load operation of an engine.

Referring to the drawings in more detail this invention may be incorporated in a fuel system 10 adapted to be employed on any type of engine 12. However in the present instance, the system 10 is particularly adapted for use on an engine 12 of the so-called spark ignited variety wherein a combustible charge of air and atomized fuel is formed and compressed in the engine cylinders and then ignited by means of an electrical discharge across a spark gap or similar element located in the engine cylinders in direct contact with the charge.

In the present instance this charge is to be formed by the fuel system 10 which meters the fuel and injects or sprays fuel under pressure into the air flowing through the induction system 14 in accordance with the fuel demands of the engine 12.

The induction system 14 may include an air intake 16 having one end thereof open to the atmosphere and a suitable arrangement of branch passages communicating with the various engine cylinders. A throttle valve 18 may be disposed in the intake 16 for controlling the volume of air flowing therepast into the engine cylinders. A restriction such as a venturi 20 may be disposed in the inlet 16 upstream of the throttle valve 18 in order to produce a pressure drop in thethroat 22 thereof indicative of the volume of air flowing therethrough and into the engine 12.

The fuel system 10, as may be seen in Figure 1, includes the following components: a supply tank 24 for the fuel, one or more pumps 26 for drawing the fuel from the tank 24 and forcing it through the system 10, a metering mechanism 28 capable of sensing the fuel requirements of the engine 12, a control valve 30 actuated by the metering mechanism 28 to control the flow of fuel through the system and a distributor 32 for dividing the fuel flow into equal increments and distributing them to the various cylinders of the engine 12.

The pump 26 may be of any design suitable for pumping a fuel such as a gasoline and in fact, if the sltuatlon Warrants it, a transfer pump and booster pump arrangement may be employed. However, the pump 26 is preferably capable of supplying the fuel in sufficient quantity and pressure to operate the injection system 10. As a practical matter it has been found preferable to employ a pump 26 having a capacity in excess of the actual fuel requirements of the engine as this not only allows the pump output to be employed for actuating various parts of the system 10, but also allows the use of a pressure relief valve 34 that will tend to maintain a predetermined fuel pressure in the fuel system 10 and thereby improve its operation. The relief valve may then spill the surplus fuel through by-pass 36 for return to the pump inlet or to the supply tank 24. It will be seen that with this type of arrangement, the pump 26 may be driven by the engine, a separate electrical motor or any other suitable means.

The metering mechanism 28 as stated before is adapted to sense the quantity of air entering the engine 12 and also the quantity of fuel entering the engine 12 and to maintain these two quantities in any desired predetermined ratio. In the present instance this metering mechanism 28 includes a substantially cylindrical diaphragm housing 38 having a plurality of diaphragms 41, 42, 43 and 44 extending transversely thereacross to form a plurality of separate chambers 45, 46, 47, 48 and 49. A rigid shaft 50 may extend axially of the housing 38 so as to interconnect all of the diaphragms 41 to 44 with each other and with a plunger 52 in a servo valve 54. It will thus be seen that the cumulative effects of the pressures on the diaphragms 41 to 44 will be effective to control the position of the servo valve 54.

In order to sense the quantity of air being consumed by the engine a tube 55 may interconnect one of the chambars 46 in the diaphragm housing 38 with the throat 22 of the venturi 20 so that one side of the air diaphragm 41 may be exposed to the throat vacuum. The chamber 45 on the opposite side of the air diaphragm 41 may be connected to the induction intake 16 or as in the present instance, it may be exposed to the atmospheric pressure. Although the former arrangement may provide a somewhat more accurate index of the quantity of air consumed, since the venturi 20 is immediately adjacent the inlet 16 to the induction system 14, there will be a negligible error in assuming that the atmospheric air pressure on the exposed side of the diaphragm 41 is equal to the air pressure immediately anterior to the venturi 20. It Will thus be seen that as the air flows into the engine 12, it will create a venturi throat vacuum so that a pressure differential will appear across the air diaphragm 41 and produce a force on the shaft 50 tending to move it toward the right with the greater the air flow the greater the force. In fact the force on the diaphragm 41 resulting from this pressure drop in the venturi 20 will be indicative of the quantity or mass of air entering the engine 12.

In order to sense the quantity of fuel being consumed in the engine 12, a restriction such as a venturi or orifice 56 may be provided in the fuel line 58, 59 and 6% so that all of the fuel entering the engine 12 will flow therethrough. Thus the fuel will produce a pressure drop thereacross which Will be indicative of the quantity of fuel consumed in the engine 12. By employing a properly designed restriction 56, this pressure drop will vary with the fuel flow in the same general fashion as the pressure 6 I drop resulting from the airflow through the venturi. A first tube 62 may be provided for interconnecting the fuel line 59 immediately anterior to the orifices 56 with the chamber 48 on one side of the fuel diaphragm 43 While a second tube 64 interconnects the chamber 47 on the opposite side of the fuel diaphragm 43 with the fuel line 60 immediately posterior to the orifice 56. It will thus be seen that the fuel flowing through the fuel line 58, 59 and 60 will produce a force on the diaphragm 43 and therefore the shaft 50 which is indicative of the quantity of fuel flowing therethrough. Since the fuel pressure on the upstream side of the restriction 56 will be the larger, the fuel pressure differential will produce a force on the shaft 50 tending to move the shaft to the left. Thus, by placing the air and fuel pressures on the correct sides of the diaphragms 41 and 43, the forces from the air pressure differential and the fuel pressure differential will oppose each other. As a result when the air and fuel are flowing in some predetermined ratio, these two resultant forces will be equal and there will be no axial force tending to move the shaft 50 in either direction. If the fuel flow is in excess of this amount or in other words the fuel flow would produce too rich a mixture, there will be a resultant force tending to move the shaft 55 to the left. flow is less than this amount or in other words would produce too lean a mixture, there will be a resultant force tending to move the shaft 50 to the right or in the opposite direction. Accordingly, it Will be seen that this diaphragm unit 51 will sense the ratio between the fuel flow and the air flow and produce a resultant force on the shaft 50 which is indicative of this ratio.

In order to maintain the air-fuel ratio at the desired amount the shaft 50 may be coupled to a control valve 30 located in the fuel line 58, 59 and 60' for controlling the flow of fuel therethrough. Although the shaft 50 could be connected directly to the control valve 30, in the present instance the shaft 50 is operatively connected to the valve 30 by a servo mechanism having a plunger 52 in a servo valve 54 which in turn is connected to a servo piston 66 on the control valve 30 by a rich line 68 and a lean line 70. These control lines 68 and 70 form ports 72 and 74 in the servo valve housing 54 and are connected to the cylinder 75 on the opposite sides of the enlargement of plunger 52 contained therein. When the air and fuel are flowing in the prescribed ratio, the resultant force on the shaft 50 will be zero and the plunger 52 will cover the ports 72 and 74. However in the event the fuel flow is too small and a lean mixture will result, the pressure drop across the fuel orifice 56 will be low. As a result the force on the air diaphragm 41 will exceed the force on the fuel diaphragm 43 and the shaft 50 will tend to move to the right. When this occurs: the plunger 52 will uncover the ports 72 and 74 and allow the pressurized fuel from the pump outlet to flow through the richer control line 68 and act on the piston 66. The exhaust fuel from cylinder 75 may be returned to tank 24 by by-pass 36. This will open the control valve 30 further. As a consequence the fuel flow to the engine 12 will increase and raise the amount of the pressure drop across the orifice 56. When the fuel flow has increased sufficiently to match the air flow, the pressure drops will return to a balanced condition so that the diaphragms will return the plunger 52 to cover the ports 72 and 74 and lock the valve 30- in its new position.

In the event that the fuel flow is too large and causes an excessively rich mixture, the fuel pressures on the diaphragms 41 and 43 will be greater than the air pressures and will cause the shaft 50 to move to the left and cause the plunger 52 to uncover the ports 72 and 74. This will allow the fuel to flow through the lean control line 70 and move the servo piston 66 to close the valve 30 and thereby decrease the fuel flow until the desired air-fuel ratio is again reestablished.

The metered fuel leaving the orifice 56 may then flow to any suitable fuel distributor 32 where it will be di- Conversely, if the fuel vided into equal portions and distributed to the various engine cylinders by the injector lines 76. Although any form of distributor 32 or flow divider may be employed, in the present instance this distributor 32 includes a rotor 78 driven by the engine at camshaft speed and having an outlet that allows the fuel to be distributed to the cylinders in intermittent intervals timed to the operation of the cylinders. Preferably the fuel is injected for a particular cylinder only during that period when the associated intake valve is open. In addition to the rotary type of distributor 32, it has been found advantageous to employ a pressure sensitive check valve 80 at the outlet end of each of the injector lines 76. This will not only insure a sharp starting and stopping of the fuel flow but also it will tend to isolate the fuel in the injection system it) from the effects of intake vacuum which would otherwise lower the pressure in the fuel system 10 sufificiently to produce a boiling of the fuel and a resultant vapor lock and/or inaccurate metering of the fuel. The check valves 80 will insure the fuel pressure remaining sufficiently high to prevent any vaporizing of the fuel.

From the foregoing it may thus be seen that in the event the throttle valve 18 is opened or closed, the volume or mass of air flowing will change. This change will be reflected in the venturi throat 22 vacuum which in turn will alter the force on the air diaphragm 41 and normally cause the shaft to move one way or the other. Movement of the shaft 50 will result in the plunger 52 moving and allowing the pressurized fuel to flow through one or the other of the ports 72 and 74 and produce movement of the servo piston 66 and the fuel control valve 30. Opening or closing movement of the control valve 30 will increase or decrease the fuel flow until the pressures on the diaphragms 41 and 43 are again balanced. As soon as this balance prevails the air and fuel flow will be in the desired proportions.

It should be noted that the foregoing system will operate satisfactorily to produce a charge having a substantially constant air-fuel mixture during all engine operating conditions. However, there may be a few minor inaccuracies that result from various factors such for example as flow losses in and around the restrictions and 56 that vary with the amount of flow therethrough. In addition, the optimum air-fuel ratio for any engine 12 may vary somewhat over its entire operating range rather than requiring an exactly constant air-fuel ratio at all times. Since the so-called road load or normal working loads on an automotive or truck engine are a small fraction of the maximum output of the engine, it is desirable to operate the engine 12 on a mixture that will result in the maximum fuel economy while driving such a load even though it may result in a slightly lower power output from the engine 12. That is to say there may be certain inaccuracies in the basic fuel metering system and/ or the maximum economy air-fuel ratio may vary slightly with the load on the engine. Accordingly, it may be desirable to modify the basic control unit to provide compensating means to correct for these factors. This may be accomplished by employing a variable metering restriction 56 in the fuel line 58, 59 and 60, as seen in Figure 2. Since varying the resistance of restriction 56 will result in a variation in the fuel pressure differential developed thereacross, this will provide an easy means of modifying the comparative effectiveness of the restrictions 20 and 55 and thus vary the air-fuel ratio.

In the present instance this variable resistance 56 includes a variable area orifice 82 mounted on a spring biased diaphragm 84- so as to be free to move. It will thus be seen when the fuel flows through the orifice 82, the opposite sides of the diaphragm 84 will be exposed to the fuel pressures anterior and posterior to the orifice 82 and a pressure differential will produce a force on the diaphragm 84 in opposition to the springs 86. A tapered stationary needle 88 may extend into the orifice 82 and thus determine the effective area of the orifice 82. Thus as the pressure drop across the orifice 82 varies, the diaphragm 84 and also the orifice 82 will move axially relative to the needle 88 and due to the taper thereof will produce a change in the area of the orifice 82. Since the amount of fuel flowing through the orifice 82 is an accurate index of the engine load, it may be seen that the area of the orifice 82 may be made to vary as a function of the load. Accordingly, the contour of the needle 88 may be tailored so that for any given engine load, the needle 88' will have a cross sectional area that provides an orifice area of any desired amount. This orifice 32 will present the prerequisite resistance for developing a pressure drop across the orifice 82 and thereby a force on the diaphragm 43 to balance the force resulting from the air flow through the venturi 20 to produce the required air-fuel ratio at that load. The continuously variable area of orifice 82 will provide a means for compensating for any operating peculiarities in the system or engine such as changes in volumetric efliciency, etc. This allows the air-fuel ratio to be maintained at any desired values during all engine operating conditions.

It may be seen that the foregoing fuel control system may be adapted to provide charges for the engine 12 having air-fuel ratios producing any desired engine operating characteristic over the entire spectrum of operation. Although in the normal automotive or truck engine it is desirable to maintain the charge at an air-fuel ratio permitting maximum fuel economy, there are frequently periods during which economy of operation is of secondary importance and maximum performance, i.e., the development of maximum torque and/or power, are the most important considerations. The normal internal combustion engine 12 when developing maximum power requires an air-fuel mixture that is somewhat richer in fuel than when it is operating at maximum economy. Accordingly, enrichment means may be provided to increase the proportion of fuel in the mixture during these periods. It will be noted that during normal operation, i.e., where economy is important, there will usually be a high intake vacuum. On the other hand where maximum performance is important, i.e., accelerating periods and full load operation, the throttle 18 will be sufficiently open and/or the air flow will be such that the intake vacuum will normally be very small. Accordingly, an enrichment or secondary metering orifice 9i) may be provided which will be controlled by the intake vacuum for producing a richer mixture. Thus the primary orifice 56 will meter the fuel during normal operating conditions, while the secondary metering orifice 90 remains inoperative, and when the maximum performance is desired, the secondary orifice 9th will become effective and modify the fuel pressure drop so as to produce a richer mixture. In the present instance as may be seen in Figure 2, this comprises a secondary metering orifice 90 in parallel with the primary metering orifice 56 with the flow therethrough being controlled by a valve 92 which is disposed inside of a housing and may be of any suitable type, is biased towards the open position by a spring 94 but is normally retained closed by the intake vacuum acting on one side of the diaphragm 96, the diaphragm 96 being interconnected with the intake manifold by tube 97. However whenever the intake vacuum decreases for example, as a result of suddenly opening the throttle valve 18, the spring 94 will overcome the effects of the vacuum and open the valve 92. This will then allow the fuel to fiow through both the primary and secondary orifices 56 and 9t], respectively. By dividing the fuel flow in this manner the pressure drop across the two parallel orifices S6 and 90 will be less than for a single orifice and as a result the control valve Siiwill be opened farther and the fuel flow increased until the forces on the diaphragms 41 and 4e are again balanced. It has been found desirable to employ a second diaphragm 98 in the valve 92 in order to balance the effects of the fuel pressure and thus make than is in the economy charge.

the valve 92 more nearly responsive to only intake vacuum.

It will thus be seen that during normal engine operation, the intake vacuum will retain the valve 92 for the secondary orifice 90 closed and thereby cause all of the metered fuel to pass through the primary orifice 56. As previously pointed out this orifice 56 may have a variable area with the cross section of the needle 88 being tailored to provide an economy mixture. However, whenever the intake vacuum is low enough, the spring 94 will open the valve 92 and allow the metered fuel to divide its flow between the primary and secondary orifices 56 and 90. This divided flow of the fuel will then result in a richer mixture suitable for maximum torque and/or power from the engine. As soon as the air flow increases or the throttle 18 is moved toward the closed position, the intake vacuum will increase and close the valve 92. This will cause all of the fuel to flow through the primary orifice 56 and thereby restore an economy fuel mixture.

When an internal combustion engine 12 is being operated with the throttle 18 closed, i.e., idling, if the mixture is as lean as is employed at part load, the engine 12 will not only have a tendency to run rough and misfire, but will also be unable to drive a load of any size. In an automotive vehicle both of these features are objectionable and accordingly, it is highly desirable to provide a charge having a considerably larger proportion of fuel Unfortunately, a fuel control system 10 that is capable of measuring the quantities of air and fuel consumed by an engine 12 operating at full load is frequently not sensitive enough to measure accurately the small quantities consumed at idle as they are too small. flow is measured by a venturi 20. If the venturi 20 is large enough to allow the full load air to flow therethrough a negligible vacuum would be developed in the venturi throat 22 at idle. Accordingly, an idle fuel control 100 may be provided that is particularly adapted to satisfy the engine fuel requirements during idling.

During idle conditions even though the vacuum developed in the venturi throat 22 will be small, the throttle valve 18 will be completely closed or nearly so. Thus the intake manifold vacuum will be high. It is therefore proposed to provide an air bleed 102 for interconnecting the intake manifold 15 with the diaphragm chamber 46 when the throttle valve 18 is at or near the closed position. Thus even though the venturi throat vacuum will be very small, there will be an adequate vacuum for retaining the fuel valve 30 sufficiently open for idle load. This bleed 102 includes arestricted orifice 104, an adjustable needle valve 106 and a control valve 108. Normally the spring 110 will hold the valve 108 closed and prevent the flow of air therethrough. As a result the air diaphragm chamber 46 will be isolated from the effects of intake vacuum when the valve 108 is closed. However, when the throttle valve 18 is in the closed position, the slack will disappear from the lost motion mechanism 111 and cause the valve 108 to open. Thus the air may be drawn from the chamber 46 and also through the needle valve 106 from whence it will pass through the orifice 104 and into the intake manifold 15. This will create a This is particularly true where the air vapors. Unless the fuel in the system 10 is isolated from the effects of this vacuum the metering system may fail to properly meter the fuel, thereby resulting in malfunctioning of the engine 12. Accordingly, a suitable pressure actuated check valve 80 may be disposed in each of the injector nozzles 79. Each of these valves 80 employs a valve member 112 and a spring 114 which biases the valve member 112 towardv the closed position. One side of each valve member 112 is exposed to intake vacuum and the other side is exposed to the fuel pressure in the injector line 76. Thus the valve 80 will be closed except when the distributor 32 directs a stream of fuel under pressure into the injector line 76 and the fuel pressure on the valve member 112 is large enough to overcome the intake vacuum and the spring 114 tension. As a result the check .valves 80 will insure the fuel pressure always being maintained sufliciently high to prevent any fuel vapors appearing in the system 10.

It should be noted when employing an arrangement of this nature the fuel pressure must overcome the intake vacuum and therefore any fluctuations in .the intake vacuum will cause a corresponding change in the fuel pressure required to open the check valve 80. Because the intake vacuum varies over a considerable range the resultant fluctuations in the fuel pressure may present serious troubles in the operation of the injection system 10. For example, if the engine is operating at or near idle conditions, the intake vacuum will be very high, the check valves will open easily, and the fuel pressure in the system will be low. If the throttle valve 18 is suddenly opened, the intake vacuum will be very small and a large fuel pressure will be required to open the check valves 80. However, since the fuel pressure has previously been very low it will be too low to properly operate the check valves 80. As a result there may be an appreciable time delay for the fuel pressure to build up, if it does so at all, and during this delay the check valves 80 will fail to open. Accordingly, the engine 12 may misfire for lack of fuel at the very time the engines fuel requirements are at a peak. To alleviate this condition, it has been found advantageous to employ a pressure relief valve 34 of the differential type at the pump 26 vacuum in the air chamber 46 that will oppose the fuel pressure drop and retain the control valve 30 positioned for correct fuel flow for idle. By opening or closing the needle valve 106 more or less air will flow through the orifice 104 and control the pressure drop thereacross and consequently, the pressure in the air chamber 46. Accordingly, the needle valve 106 will control the airfuel ratio at idle.

As previously stated it has been found that while operating the engine 12, the vacuum in the intake manifold 15 frequently becomes very high and will tend to have a very pronounced effect on the rate of discharge of fuel from the injector nozzles 79. Also under some conditions thisvacuum is so high that the fuel will flash or boil into outlet. In addition to have a spring 116 for controlling the fuel pressure, a diaphragm 118 may be provided which is connected to tube 97 and responsive to the intake vacuum. In the event the fuel pressure is too low for the intake vacuum, the spring 116 will close the valve 34 thus insuring the regulated fuel pressure instantly building up to the desired amount. It will thus be seen that the relief valve 34 will provide a pressure in the fuel system 10 that is dependent upon the intake vacuum and is the optimum amount thereabove for proper operation of the check valves 80. As a result the fuel pressure at the nozzles 79 will always be sufiiciently high to insure proper injection of the fuel at all times irrespective of the variations in the intake vacuum.

' Summary of operation During idle operation of the engine 12 the throttle valve 18 will be closed and a very limited amount of air will be drawn into the engine 12. Accordingly, very little, if any, vacuum will be apparent in the throat 22 of the venturi 20. The pump 26 will deliver its output to the servo valve 54, the control valve 30, and the relief valve 34 which will maintain the fuel pressure in the system sufficiently high to insure proper operation thereof. Since the intake vacuum is highest at this time the relief valve 34 will maintain the fuel pressure at its lowest value. However, such fuel flow as there is will flow entirely through the variable area orifice 56, the area of which is very small, and then to the distributor 32 and the various nozzles 79. Since the high intake vacuum will maintain the secondary orifice closed, all of the pressure will appear across orifice 56 and the fuel diaphragm 43 and tend to close the control valve 30. At the same time the fuel flow will be very small and so the valve 30 will be practically closed. The throttle 18 being closed, the lost motion mechanism will open the valve 108, thereby allowing the air in the diaphragm chamber 46 and atmospheric air to be drawn through the orifice 104. The air flow through the orifice 104 will cause a pressure drop which is easily regulated by means of the needle valve 106. Thus the needle valve 1% may be set so that the vacuum in the chamber 46 will oppose the fuel pressure and open the control valve 30 until the desired fuel flow is obtained. It should be noted that when the idle control 100 is operative the fuel flow is substantially independent of the air flow. However, when the throttle 18 is closed air flow is substantially the same within narrow limits regardless of the engine load. Accordingly, even through the quantity of fuel flow at idle will always be the same, by properly adjusting the needle valve 106 the fuel flow will be adequate to maintain the air-fuel ratio suificiently rich to insure operation of the engine.

When it is desired to have the engine 12 carry a load, for example, driving an automotive vehicle, the throttle 18 will be partially opened and the engine 12 will be operating at so-called road load. At this time there will be an adequate volume of air flow through the venturi 20 to create a suflicient vacuum in the venturi throat 22 to insure a positive operation of the metering unit 28. Therefore, the lost motion mechanism 111 will allow the spring 114) to close the valve 108. Thus the idle system 100 will be inoperative and the air chamber 46 will be isolated from the intake vacuum and subject to venturi throat vacuum. At this time the pump output will still be delivered to the servo valve 54, the control valve 30, and the pressure relief valve 34. However, since the intake vacuum will be somewhat less than during idle operation, the relief valve 34 will maintain a somewhat higher fuel pressure in the system It). The fuel from the control valve 30 will then flow through the variable or primary metering orifice 56 and to the distributor 32 and injector nozzles 79. It should be noted that in this load range the pressure drop across the orifice 82 will be high enough to cause a limited compression of the springs 86 and axial movement of the orifice 82 relative to the needle 88. Preferably, the area of the orifice 82 is suitable for maximum economy charging of the engine 12 with the needle 88 being contoured only to compensate for any peculiarities in the engine 12 and/ or the system 10. It should be noted that since the intake vacuum is still comparatively high, the valve 92 will remain closed and there will be no fuel flow through the power enriching or secondary metering orifice 90. Consequently, all of the metered fuel will flow through the primary or variable metering orifice 56 and develop a pressure drop thereacross which will be directed to the opposite sides of the fuel diaphragm 43. This pressure drop will provide an axial force on the shaft 50 in opposition to the force resulting from the air pressure drop. These two forces as previously stated will caused operation of the servo valve 54, servo piston 66 and control valve 3% until the two forces are balanced and the control valve 30 remains stationary. It may thus be seen that during the normal road load operating range the variable area orifice 56 will insure an economical charge being maintained at all times.

If the load on the engine 12 is increased by a sudden opening of the throttle valve 18 or if the engine 12 is operating at full load with the throttle valve 18 substantially fully open, the intake vacuum will be very small. However, the volume of air flow and the volume of fuel flow will be considerable. Since the intake vacuum will be very small, the spring 94 will open the enrichment valve 92 and allow fuel to flow through the secondary metering orifice 90 in addition to the primary orifice S6 and also the relief valve 34 will cause a high pressure in the fuel system. In addition, there will be a large vacuum in the venturi throat 22 which will tend to completely open the control valve 30. This fuel will then divide 12 and a portion will flow through the variable area orifice 56 and a portion through the secondary orifice 90. The fuel will then recombine and flow through the distributor 32 and nozzles 79. Since the fuel is flowing through both of the orifices 56 and 90, the pressure drop thereacross will be less than if it all flowed through the primary orifice 56 only. As a result the pressure on the fuel diaphragm 43 will be smaller and provide less opposition to the force from the air diaphragm 41. Consequently, the servo valve 54, servo piston 66 and control valve 30 will all have to cooperate with each other to increase the 7 fuel flow slightly and produce a somewhat richer mixture.

It should be noted that although the variable area orifice 56 will be at its peak area and both metering orifices 56 and $0 are in operation, the system will function in an identical manner to balance the two pressure differentials. However, because of the two orifices, the maximum power charge will be provided.

It is to be understood that, although the invention has been described with specific reference to a particular embodiment thereof, it is not to be so limited since changes and alterations therein may be made which are within the full intended scope of this invention as defined by the appended claims.

I claim:

1. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential indicative of the quantity of air flowing therethrough and a throttle for controlling said flow, a fuel system including a source of pressurized fuel having a fuel line with a restriction therein to produce a pressure drop indicative of the quantity of fuel flowing therethrough, said restriction including a pair of orifices for said fuel to flow therethrough, only one of said orifices normally being inoperative, and a control unit for varying said fuel flow through said last mentioned restriction to maintain a predetermined relationship between said pressure differentials, means responsive to the intake vacuum in said induction system and being effective to actuate said second orifice only during certain vacuum conditions to cause a modification of the charge during such conditions.

2. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure difierential proportional to the quantity of air flowing therethrough and a throttle for controlling said flow, a fuel system including a fuel line with a restriction therein comprising a pair of metering orifices disposed therein in parallel relationship to produce a pressure differential indicative of the quantity of the fuel flow, a control unit responsive to said pressure differentials for varying the flow of fuel through said fuel line to thereby maintain said pressure differentials in some predetermined relation, and means responsive to the load on said engine for causing one of said orifices to remain inoperative except during certain operating conditions, the other of said orifices having a variable area over the entire operating range of said engine.

3. Charge forming means. for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential proportional to the quantity of air flowing therethrough and a throttle for controlling said flow, a fuel system including a fuel line having a first normally operative metering orifice therein and a second normally inoperative metering orifice disposed therein in parallel relation to said first orifice whereby the fuel flow in said fuel line will create a pressure differential indicative of the fuel flow therethrough, means responsive to the intake vacuum in said induction system for causing said second orifice to become operative during certain engine ond pressure differential, and a control unit responsive to 13 said pressure differentials and effective to vary said fuel flow to maintain said pressure differentials in some predetermined proportions.

4. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential indicative of the quantity of air flowing therethrough and a throttle valve for controlling said flow therein, and a fuel system for mixing fuel in said air to form a charge and having a source of pressurized fuel with a fuel line having a restriction therein comprising a pair of orifices disposed in parallel to allow the fuel flowing to the engine to divide therebetween and develop a pressure differential indicative of the total fuel flow to the engine, a fuel valve disposed in said fuel line for varying said fuel flow therethrough, a control unit comprising a pair of pressure responsive elements, one of which is responsive to said induction pressure differential and the other of which is responsive to the said fuel pressure differential across said pair of orifices, said control unit being operatively interconnected with said fuel valve to maintain said pressure differentials in some predetermined proportion, normally closed valve means disposed in series with only one of said parallel orifices to normally force the fuel flow through only one of said orifices and to open said second orifice only during certain engine operating conditions to modify the fuel pressure differential to thereby vary the mixture ratio of the resultant charge.

5. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential indicative of the quantity of air flowing therecontrolling the flow of fuel through said fuel restriction for maintaining a predetermined relationship between said pressure differentials, a valve disposed in series with one of said parallel orifices, said valve when in the open position allowing fuel to flow through both orifices and when in the closed position forcing all of the fuel to flow through only one of said orifices, and means responsive to the intake vacuum to open said valve only when said vacuum is less than some predetermined amount to modify said fuel pressure differential and thus vary the air-fuel ratio of the resultant charge.

7. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential proportional to the quantity of air flowing therethrough and a throttle for controlling said flow, a fuel system including a source of pressurized fuel having a fuel line with a restriction therein to produce a pressure differential indicative of the quantity of fuel flowing therethrough and a control unit for varying te flow of fuel through said fuel restriction to thereby maintain a predetermined relationship between said pressure differentials, said last mentioned restriction including a first orifice that remains open at all times with the area thereof varying through and a throttle for controlling said flow therein,

a fuel system for mixing fuel with said air to form a combustible chargeand including a source of pressurized fuel having a fuel line with a restriction therein comprising a pair of orifices disposed in parallel to allow the fuel flow to the engine to divide therebetween and develop a pressure differential indicative of the total fuel flow to the engine, a fuel valve disposed in said fuel line for varying said fuel flow therethrough, a control unit having a pair of pressure responsive elements, one of which is responsive to said induction pressure differential and the other of which is responsive to said fuel pressure differential across said pair of orifices, said fuel valve being operatively interconnected with said control unit for varying the flow of fuel through said fuel line for maintaining a predetermined relationship between said pressure differentials, normally closed valve means disposed in series with one of said parallel orifices to normally force the fuel flow through only one of said orifices, and means responsive to the intake vacuum to open said normally closed valve only during some predetermined vacuum conditions to modify said fuel pressure differential and thus vary the air-fuel ratio of the resultant charge during such conditions.

6. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure diiferential indicative of the quantity of air flowing therethrough and a throttle for controlling said flow therein, a fuel system for mixing fuel with said air to form a combustible charge and including a source of pressurized fuel having a fuel line with a restriction therein comprising a pair of orifices disposed in parallel to allow the fuel flow to the engine to divide therebetween and develop a pressure difierential indicative of the total fuel flow to the engine, a fuel valve disposed in said fuel line for varying said fuel flow therethrough, a control unit having a pair of pressure responsive elements, one of which is responsive to said induction pressure differential, and the other of which is responsive to the fuel pressure differential across said pair of orifices, said control unit being operatively interconnected with said fuel valve for as a function of the load on said engine and a second orifice that normally remains inoperative but becomes operative during certain engine operating conditions to thereby modify the fuel pressure differential during such conditions.

8. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential proportional to the quantity of air flowing therethrough and a throttle for controlling said flow, a fuel system including a fuel line with a restriction therein comprising a pair of metering orifices disposed in said line in parallel relationship to produce a single fuel pressure differential indicative of the quantity of fuel flowing therethrough, a control unit responsive to said pressure differentials for varying the flow of fuel through said fuel line to thereby maintain said pressure differentials in some predetermined relation, means responsive to the load on said engine for varying the area of one of said orifices as a function of said load, and additional means responsive to the load on said engine for causing the other of said orifices to remain inoperative except during certain engine operating conditions.

9. Charge forming means for an internal combustion engine comprising an induction system with a venturi inlet having a restricted throat therein adapted to produce a pressure differential indicative of the quantity of air flowing therethrough and a throttle for controlling said flow, a fuel system for mixing fuel with said air to form a combustible charge and including a source of pressurized fuel having a fuel line with a restriction therein comprising a pair of orifices disposed in parallel to allow the fuel flow to the engine to divide therebetween and develop a pressure differential indicative of the total flow to the engine, a fuel valve disposed in said fuel line for varying said fuel flow therethrough, a control unit having a pair of pressure responsive elements, one of which is responsive to said induction pressure differential and the other of which is responsive to said pressure differential across said pair of orifices, said control unit being operatively interconnected with said fuel valve for varying the flow of fuel through said fuel line for maintaining a predetermined relationship between said pressure differentials, one of said orifices including means for varying the area thereof in proportion to the flow of fuel therethrough, normally closed valve means disposed in series with the other of said orifices to normally force all of the fuel to flow through only said variable area orifice, and means responsive to the intake vacuum in said induction system to open said normally closed valve only during some predetermined vacuum conditions to modify said fuel pressure differential 15 and thus vary the, air-fuel ratio of the resultant charge during such conditions.

10. a fuel system adapted to be employed on an internal combustion engine, said fuel system comprising a control having one portion thereof responsive to a pressure differential indicative of air flowing into said engine and having another portion thereof responsive to a pressure differential indicative of fuel flowing into said engine and being effective for varying said fuel flow to maintain said pressure differentials in a predetermined relation, and means for interconnecting said control with the engine intake vacuum for modifying said first pressure differential whenever it is less than some predetermined amount.

11. A fuel system adapted to be employed on an internal combustion engine having an induction system with a throttle for controlling the quantity of air flowing therethrough, said fuel system comprising a control with one portion thereof responsive to a first pressure differential indicative of said air flow and another portion thereof responsive to a second pressure differential indicative of fuel flowing into said engine, means actuated by said control for varying the fuel flow to maintain said pressure differentials in a predetermined relation, and means for interconnecting said control with said induction system posterior to said throttle whenever said throttle approaches the closed position to thereby modify said first pressure differential.

12. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential proportional to the quantity of air flowing therethrough and a throttle for controlling said flow of air, a fuel system including a source of pressurized fuel having a fuel line with a restriction therein to create a pressure differential indicative of the quantity of fuel flowing therethrough, a control valve in said fuel line for controlling the flow of fuel through said line and said restriction, a first pressure element responsive to the pressure differential in said inlet and a second pressure element responsive to the pressure differential across said fuel restriction, said elements being interconnected with said control valve to vary the fuel flow and maintain said pressure differentials in some predetermined proportions, means for interconnecting one of said pressure responsive elements with said induction system whenever said air flow is less than a predetermined amount for modifying the effectiveness of said first pressure differential.

13. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential proportional to the quantity of air flowing therethrough and a throttle for controlling said fiow of air, a fuel system including a source of pressurized fuel having a fuel line with a restriction therein to create a pressure differential indicative of the quantity of fuel flowing therethrough, a control valve in said fuel line for controlling the flow of fuel through said line and said restriction, a first pressure element responsive to the pressure differential in said inlet and a second pressure element responsive to the pressure differential across said fuel restriction, said pressure responsive elements being interconnected with said control valve to vary the fuel flow and maintain said pressure differentials in some predetermined proportions, an air bleed for interconnecting the first of said pressure responsive elements with said induction system whenever said air flow is less than a predetermined amount for modifying the effectiveness of of said pressure differential, and an adjustable vent open to the atmosphere for controlling the amount of intake vacuum transferred to said pressure responsive element.

14. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential proportion to the quantity of air flowing therethrough and a throttle for controlling said flow of air, a

fuel system including a source of pressurized fuel having a fuel line with a restriction therein to create a pressure differential indicative of the quantity of fuel flowing therethrough, a control valve in said fuel line for controlling the flow of fuel through said line and said restriction, a first pressure element responsive to the pressure differential in said inlet and a second pressure element responsive to the pressure differential across said fuel restriction, said elements being interconnected with said control valve to vary the fuel flow and maintain said pressure differentials in some predetermined proportions, an air bleed having a metering orifice therein interconnecting one of said pressure responsive elements with said induction system, a normally closed valve disposed in said air bleed for isolating said pressure responsive element from said induction system, said valve being adapted to open only during certain engine operating conditions to expose said last mentioned pressure responsive element to the intake vacuum in said induction system.

15 Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential proportional to the quantity of air flowing therethrough and a throttle for controlling said flow of air, a fuel system including a source of pressurized fuel having a fuel line with a restriction therein to create a pressure differential indicative of the quantity of fuel flowing therethrough, a control valve in said fuel line for controlling the flow of fuel through said line and said restriction, a first pressure element responsive to the pressure differential in said inlet and a second pressure element responsive to the pressure differential across said fuel restriction, said elements being interconnected with said control valve to vary the fuel flow and maintain said pressure differentials in some predetermined proportions, an air bleed interconnecting said first pressure responsive means with said induction system, a normally closed valve disposed in said air bleed for controlling the flow therethrough and means responsive to the quantity of air entering the engine to be effective to open said valve only when said first pressure differential is less than some predetermined amount.

16. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential proportional to the quantity of air flowing therethrough and a throttle for controlling said fiow of air, a fuel system including a source of pressurized fuel having a fuel line with a restriction therein to create a pressure differential indicative of the quantity of fuel flowing therethrough, a control valve in said fuel line for controlling the flow of fuel through said line and said restriction, a first pressure element responsive to the pressure differential in said inlet and a second pressure element responsive to the pressure differential across said fuel restriction, said elements being interconnected with said control valve to vary the fuel flow and maintain said pressure differential in some predetermined proportions, an air bleed having a metering orifice therein interconnecting said first pressure responsive means with said induction system posterior to said throttle, a normally closed valve disposed in said air bleed for controlling the flow of air therethrough, a lost motion linkage on the throttle adapted to open said valve as said throttle approaches the idle position.

17. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential proportional to the quantity of air flowmg therethrough and a throttle for controlling said flow of air, a fuel system including a source of pressurized fuel having a fuel line with a restriction therein to produce a pressure differential proportional to the quantity of fuel 17 flowing therethrough and a valve therein for controlling said flow of fuel, a control unit having a plurality of pressure responsive diaphragms forming a plurality of chambers which are interconnected with said induction system and fuel system and being operatively connected to said valve for maintaining said pressure differentials in some predetermined proportions, an air bleed interconnecting one of said chambers with said induction system and means responsive to the air flow through said induction system for closing said air bleed for isolating said last mentioned chamber from intake vacuum except when said first pressure differential is greater than some predetermined amount.

18. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential proportional to the quantity of air flowing therethrough and a throttle for controlling said flow of air, a fuel system including a source of pressurized fuel having a fuel line with a restriction therein to produce a pressure differential proportional to the quantity of fuel flowing therethrough and a valve therein for controlling said flow of fuel, a control unit having a plurality of pressure responsive diaphragms forming a plurality of chambers which are interconnected with said induction system and fuel system and being operatively connected to said valve for maintaining said pressure differentials in some predetermined proportions, an air bleed interconnecting one of said chambers with said induction system posterior to said throttle, a control valve in said bleed effective to isolate said chamber from the effects of intake vacuum, means responsive to the position of said throttle for opening said control valve as said throttle approaches the closed position.

19. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a restriction therein adapted to produce a pressure differential proportional to the quantity of air flowing therethrough and a throttle for controlling said flow of air, a fuel system including a source of pressurized fuel having a fuel line with a restriction therein to produce a pressure differential proportional to the quantity of fuel flowing therethrough and a valve therein for controlling said flow of fuel, a control unit having a plurality of pressure responsive diaphragms forming a plurality of chambers which are interconnected with said induction system and said fuel system and being operatively con- I nected to said valve for maintaining said pressure differentials in some predetermined proportions, an air bleed interconnecting one of said chambers with said induction system posterior to said throttle, a control valve responsive to the position of said throttlefor closing said air bleed whenever said throttle is at least partially open, and vent means in said air bleed open to the atmosphere for determining the amount of vacuum developed in said chamber when said control valve is open.

20. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a venturi forming a restricted throat to produce a pressure differential proportional to the quantity of air flowing therethrough and a throttle for controlling said flow of air, a fuel system including a source of pressurized fuel having a fuel line with a restriction therein to produce a pressure differential proportional to the quantity of fuel flowing therethrough and a valve therein for controlling said flow of fuel, a control unit having a plurality of pressure responsive diaphragms forming a plurality of chambers, the chambers on the opposite sides of one of said diaphragms being interconnected with said fuel line on the opposite sides of said restriction to subject said last mentioned diaphragm to said pressure differential, a chamber on one side of another diaphragm being interconnected with the throat of said venturi to subject said last mentioned diaphragm to said first mentioned pressure differential, an air bleed interconnecting said last mentioned chamber with said induction system posterior to said throttle and means rseponsive to the air flow through ,saidinduction system for closing said air bleed vacuum except when said first pressure differential is greater than some predetermined amount.

21. Charge forming means for an internal combustion engine comprising an induction system having an inlet with a venturi forming a restricted throat to produce a pressure differential proportional to the quantity of air flowing therethrough and a throttle for controlling said flow of air, a fuel system including a source of pressurized fuel having a fuel line with a restriction there in to produ ce a-pressure differential proportional to the quantity.

of fuel flowing therethrough and a valve therein f or controlling said flow of fuel, a control unit having a plurality of pressure responsive diaphragms forming a plurality of chambers, the chambers on the opposite sides of one of said diaphragms being interconnected with said fuel line on the opposite sides of said restriction to subject said last mentioned diaphragm to said pressure difierential, a chamber on one side of another diaphragm being interconnected with the throat of said venturi to subject said last mentioned diaphragm to said first mentioned pressure differential, an air bleed interconnecting said last mentioned chamber with said induction system posterior to said bottle and lost motion means actuated by said throttle for opening said control valve only when said throttle is approaching the closed position.

22. The combination of claim 21 wherein said air bleed includes an adjustable atmospheric vent for controlling the amount of vacuum transferred to said chamber when said control valve is in the open position.

23. Charge forming means for an internal combustion engine adapted to consume a combustible charge of air and fuel, said means comprising an induction system having a throttle for controlling the flow of air therethrough, a fuel system having a source of pressurized fuel, means for metering said fuel in some predetermined relationship to said air, distributing means for distributing said metered fuel to said induction system of said engine, and means for maintaining a substantially constant pressure difierence between the pressure of the fuel in said fuel system and the pressure of the air in said induction system.

24. Charge forming means for an internal combustion engine having a plurality of cylinders adapted to consume a combustible charge of air and fuel, said charge forming means comprising an induction system communi eating with said cylinders to charge them and a throttle for controlling the volume of said charge, a fuel system having a pump for circulating fuel under pressure through said system to be mixed with said air and to form said charge, means for metering said fuel in some predetermined relationship to the volume of said air, distributing means for distributing said metered fuel to said induction system, said distributing means including injector nozzles disposed in said induction system adjacent said cylinders, and a pressure relief valve responsive to the intake vacuum for maintaining a predetermined pressure differential between the pressure of.said fuel in said fuel system and the pressure of the air in said induction system.

25. Charge forming means for an internal combustion engine having a plurality of cylinders adapted to consume a combustible charge of air and fuel, said charge forming means comprising an induction system communicating with said cylinders to charge them and a throttle for controlling the volume of said charge, a fuel system including a fuel pump for circulating fuel under pressure through said system to be mixed with said air to form said charge, means for metering said fuel in some predetermined relationship to the volume of said air, distributing means for distributing said metered fuel to said induction system, said distributing means including injector nozzles having a check valve disposed in said induction system with a pressure relief valve communicating with said pump out-' let and responsive'to the intake vacuum for maintaining a predetermined pressure differential between the pressure of said fuel in said system and the air in said induction system.

26. A fuel system adapted to be employed on an internal combustion engine having an induction system with a throttle for controlling the quantity of air flowing therethrough, said system comprising a control responsive to a pressure signal indicative of said air flow and responsive to the fuel flowing into said engine, means actuated by said control for varying the fuel flow to maintain said air, and fuel in a predetermined relation, means for interconnectingsaid control with said induction system pos-l teriorto said throttle whenever said throttle "approaches the closed, position to thereby modify said pressuresignal.

References Cited in the file of this patent UNITED STATES PATENTS 2,281,411 Campbell Apr. 28, 1942 2,447,261 Mock Aug. 17, 1948 2,447,265 Beardsley Aug. 17, 1948 2,447,267 Mock Aug. 17, 1948 2,455,308 Lee Nov. 30, 1948 2,482,956 Wirth et a1 Sept. 27, 1949 Nystrom et a1 Dec. 4, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nea 22,899,948 August 18, 1959 Rom-11d Co Groves It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should readas corrected below.

Column line 58,, for total flow" read total fuel 10 column 18, line 2'7, for "bottle" read me throttle Signed and sealed this 31st day oi May 1960.,

SEAL) Attest:

KARL Hm AXLINE ROBERT C. WATSON Attesting Ofiiccr Commissioner of Patents 

